1) Field of the Invention
The present invention relates to the downsizing of a feeder, which includes both of a feed unit and a re-feed unit.
2) Description of the Related Art
A conventional image forming apparatus (such as a copying machine and a printer) is provided with a feeder on the side of the apparatus. The feeder includes a feed unit as a manual feed mechanism and a re-feed unit as a paper reversing mechanism. In such a feeder, generally, the re-feed unit is positioned in the upper portion thereof, and the feed unit is positioned below the re-feed unit (for example, see Japanese Patent Application Laid-Open No. 2000-309451).
FIG. 9 is a schematic diagram of a conventional paper feeding device 208 fitted to an apparatus main unit 5.
A paper reversing mechanism 6 includes a reversing path 23, a reversing roller pair 25 which rotates bidirectionally, a paper re-feed path (re-feed path) 24, and a first feed roller pair 28 near the end of the re-feed path 24. When a recording medium (such as a sheet of paper) with a toner image formed on one side thereof is fed to the reversing path 23, transport of the recording medium is suspended at a position where the rear end (i.e. opposite side with respect to the feed direction) of the recording medium is clamped between the reversing roller pair 25. Thereafter, the reversing roller pair 25 is reversely rotated, to send off the recording medium from the reversing path 23. The recording medium is carried through the re-feed path 24, and re-fed to the printer engine 2 which forms a toner image on the other side of the recording medium. When the printer engine 2 does not form the toner image on the other side, the recording medium is only turned out and ejected onto a paper ejection tray (not shown).
A manual feed mechanism 7 includes a manual feed tray 32, a manual paper feed path (feed path) 33, and a paper feed roller pair (second feed roller pair) 36. The recording medium on the manual feed tray 32 is carried through the manual paper feed path 33 to the paper feed roller pair 36, which is rotated to feed the recording medium to the printer engine 2 in the apparatus main unit 5.
Recently, with the downsizing of the apparatus main unit 5, the paper reversing mechanism 6 and the manual feed mechanism 7 are desired to be as close as possible to each other to downsize the paper feeding device 208. However, there is a limitation on the arrangement of the mechanisms 6 and 7 because the first feed roller pair 28 in the paper reversing mechanism 6 and the paper feed roller pair 36 in the manual feed mechanism 7 should not contact to each other. Therefore, it is difficult to reduce the size of the paper feeding device 208 further than that described in Japanese Patent Application Laid-Open No. 2000-309451.
The size of the paper feeding device 208 can be reduced by removing either one of the first feed roller pair 28 and the paper feed roller pair 36. However, this approach deteriorates the feeding performance of the recording medium, causing a problem that the recording medium is not stably fed to the printer engine 2. There is another problem that the feedable size of the recording medium is restricted. That is, for example, if the first feed roller pair 28 in the paper reversing mechanism 6 is removed, a recording medium having a length shorter than the interval between a carrier roller pair 27 and the resist roller pair 11 cannot be carried in the paper reversing mechanism 6.
Alternatively, the size of the paper feeding device 208 can be reduced by providing, as shown in FIG. 10, a common roller pair 328 which functions as both the first feed roller pair 28 and the paper feed roller pair 36. However, the angle of the re-feed path 24 toward the common roller pair 328 is quite different from the angle of the manual paper feed path 33 toward the common roller pair 328. As a result, if the nip direction of the common roller pair 328 is adjusted for the recording medium fed from the re-feed path 24, the nip direction is not appropriate for the recording medium fed from the manual paper feed path 33, unstabilizing the transport of the recording medium from the manual paper feed path 33. Similarly, if the nip direction is adjusted for the recording medium fed from the manual paper feed path 33, the nip direction is not appropriate for the recording medium fed from the re-feed path 24, unstabilizing the transport of the recording medium from the re-feed path 24. It is possible to make the above angles as close as possible, however, this causes another problem that the paper feeding device 208 becomes large, since the re-feed path 24 and the manual paper feed path 33 cannot be bent largely from the standpoint of stable transport.